1. Field of the Invention
This invention relates to an improved process for the chemical separation of uranium isotopes by using an anion exchanger.
More particularly, this invention relates to a process for separating uranium isotopes by oxidationreduction chromatography through an anion exchanger in which both a deactivated oxidizing agent and a deactivated reducing agent are regenerated with an anion exchanger used for the separation of uranium isotopes.
2. Description of the Prior Art
It is known that uranium isotopes can be separated by developing a uranium adsorption zone on an anion exchanger as the adsorbent in its displacing state while oxidizing the uranium adsorption zone at its frontal region and reducing the uranium adsorption zone at its rear region (see British Pat. No. 1,443,962, U.S. Pat. Nos. 4,049,769, 4,092,398, 4,112,044 and 4,118,457). According to these methods a relatively high efficiency of separating uranium isotopes can be obtained.
According to one conventional process for separating uranium isotopes by an oxidation-reduction reaction using an anion exchanger, a solution containing an oxidizing agent which is capable of oxidizing uranium (IV) to uranium(VI) is supplied to a developing column packed with an anion exchanger to form an oxidizing agent adsorption zone, followed by supplying a uranium isotope solution containing uranium (IV) to convert a portion of oxidizing agent adsorption zone to an adsorbed uranium (VI) zone and then supplying a solution containing a reducing agent which is capable of reducing uranium (VI) to uranium (IV) to reduce uranium (VI) absorbed on the anion exchanger to be eluted in the form of uranium (IV)
Thus, a boundary is formed between the oxidizing agent zone and the uranium adsorption zone in the front portion, in the direction of flow, of the uranium adsorption zone, and the uranium solution recovered from the vicinity of this boundary has a higher concentration of uranium-238. Also, a boundary is formed between the uranium adsorption zone and the reducing agent zone in the rear portion, in the direction of flow, of the uranium adsorption zone, and the uranium solution recovered from the vicinity of this boundary has a higher concentration of uranium-235.
In this separation of uranium isotopes it is also known that more than one developing column filled with an anion exchanger may be employed, and the eluted solution containing uranium (IV) is fed from one developing column to the next packed with an anion exchanger where an oxidizing adsorption zone is already formed, thereby continuously forming a uranium adsorption zone, and then passing a solution containing a reducing agent therethrough.
In these operations uranium atoms should be in an anionic form. Uranium ion which is not coordinated with a ligand is usually in a cationic form. Thus, a uranium cation is converted to a uranium anion by forming complex compounds with negatively charged ligands. As used herein and in the appended claims, the term "uranium (IV)" denotes all tetravalent uranium ions including complex ions, and the term "uranium (VI)" denotes all hexavalent uranium ions including complex ions
In these operations, a deactivated oxidizing agent and a deactivated reducing agent are eluted as a mixture from a developing column.
A method for regenerating a deactivated oxidizing agent and a deactivated reducing agent in the eluant from a developing column and for reusing them is disclosed in USP No. 4,202,860.
According to the method, an eluant containing a deactivated oxidizing agent and a deactivated reducing agent is subjected to an oxidation reaction to activate the deactivated oxidizing agent, the activated oxidizing agent is separated from the resulting eluant, then the resulting eluant containing the deactivated reducing agent is subjected to a reduction reaction to activate the deactivated reducing agent, and the activated oxidizing agent and the activated reducing agent thus obtained are reused, respectively, for further separation of uranium isotopes.
In this process, the activation of the deactivated oxidizin,g agent or the deactivated reducing agent is carried out by oxidation-reduction reaction using oxygen or hydrogen, or by electrolysis oxidation-reduction reaction outside the developing column.